HR: 1340h
AN: H43F-0416    [Abstracts]
TI: INFLUENCE OF FRACTURE INTERSECTIONS UNDER UNSATURATED, LOW FLOW CONDITIONS
AU: Wood, T R
EM: tqw@inel.gov
AF: INEEL, PO BOX 1625, Idaho Falls, ID 83415 United States
AU: * Nicholl, M
EM: michael.nicholl@ccmail.nevada.edu
AF: UNLV, 227 LFG, Las Vegas, NV 89122 United States
AU: Glass, R J
EM: rjglass@sandia.gov
AF: Sandia National Laboratories, Flow Visualization and Flow Processes, Albuquerque, NM 87185 United States
AB: Recent experimental evidence suggests that the capillary heterogeneity associated with fracture intersections can act to impose temporal and spatial structure on network-scale flows. A simple intersection between orthogonal fractures, one horizontal and the other vertical, has been shown to integrate unsaturated flows. At low flows, the intersection forms a capillary barrier that accumulates water in a growing pool. Eventually the retaining meniscus snaps, discharging a pulse of water. Here, we develop a mechanistic explanation for this observed behavior and experimentally consider three perturbations to the geometry of the simple orthogonal intersection. Two of the perturbations also act as capillary barriers, while the third formed a capillary bridge across the intersection. At low flow, all of our experimental intersections imposed a temporal signal, with the nature of that signal dependent on intersection geometry and participation by the horizontal fractures in dynamic storage. At high flow, a continuous fluid tendril spanned the system from inlet to outlet with water pooled above the intersection caused by a narrow fluid connection that restricted flow across the intersection. Results from all experiments suggest that pulsation is critically sensitive to small variations in the geometry of fracture intersections, which can generate pulsation of flow across wide time periods and discharge volumes.
DE: 1894 Instruments and techniques
DE: 1829 Groundwater hydrology
DE: 1875 Unsaturated zone
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting